1. Field of the Invention
The present invention relates to a method of cooling a charge or batch, especially of metal workpieces, after thermal treatment within a closed chamber by blowing in a cooling gas. The present invention also relates to oven or kiln equipment for carrying out such a method.
2. Description of the Prior Art
For a long time, the "new" method of so-called vacuum hardening has been a conventional method for hardening metallic workpieces. This method essentially comprises heating the material which is to be treated (the charge) under vacuum to the required hardening temperature, and subsequently quenching the charge by blowing in a cooling gas, such as nitrogen or argon. The advantages which such a method offers, especially with regard to the surface quality of the hardened material, however, cannot be utilized if the quenching process within the charge takes place so non-uniformly that greatly differing hardness values result therefrom, or if on an individual piece, which is being handled, notable temperature differences occur between different spots of the piece being treated, which can lead to permanent changes in shape (distortion). Such shortcomings can be intensified if the individual parts being treated, or the entire charge, have different mass distributions, or if, due to the build-up of the charge, the flow through of cooling gas is obstructed.
It is an object of the present invention, for cooling a charge subsequent to thermal treatment within a closed chamber of oven equipment by blowing in cooling gas, to develop a method which offers the possibility of allowing the cooling of a charge to take place as a function of the actual conditions at a predetermined velocity, and according to which at the same time it is possible to maintain a uniform temperature distribution within the charge.
It is a further object of the present invention to provide oven or kiln equipment for carrying out such a method.